A major goal of developmental biology is to define the molecular program and patterning principles involved in the process of organogenesis. This interest has been fueled in recent years by the growing necessity to find alternative sources for human organs, as there is a worldwide shortage of donor organs for transplantation. While the acceleration of advances in stem cell research is encouraging, our ability to manipulate the process of organogenesis hinges on our understanding of the molecular programs and patterning principles involved. The branched tubular network is the most common structural design of organs, employed by vasculature, glandular and pulmonary systems alike. The branching pattern of the network and the proper sizes and shapes of the constituent tubes are critical for organ function. The Drosophila tracheal respiratory system is a paradigm for understanding the development of branched tubular networks, as the molecular program controlling development of the Drosophila trachea has been elucidated by systematic genetic analysis. Over a hundred genes necessary for tracheal development have been identified, and this wealth of genetical and molecular information makes the trachea an ideal model system to attempt the next step of understanding organogenesis - reconstructing and manipulating this process in vitro. Towards this long-term goal, my specific aims are: (1) to determine whether the expression of the known set of early tracheal transcription factors can induce full repertoire of early tracheal gene expression in naive embryonic cells in vivo;(2) to determine whether the expression of the known set of early tracheal transcription factors can reprogram differentiated cells in vivo and cultured Drosophila cells to a tracheal fate;(3) to determine whether cells reprogrammed to a tracheal fate can form tracheal tubes and branched structures in vitro. If these aims are successful, I will have established an in vitro system of tubular morphogenesis based on the normal developmental program, which will provide an accessible system for analysis of downstream morphogenesis events and will open up a developmental genetics-based approach to tissue engineering.